Method and apparatus to relieve the strain on roller apron segments during continuous casting

ABSTRACT

In a continuous casting machine in which the casting emerging from the mold is conducted through a secondary cooling zone by a guide apron having spaced apron segment parts between which the casting moves, means are provided for relieving overload stresses which may be applied to said spaced apron segment parts by said casting in the event of interruption of the casting process. Hydraulic pressure is applied to said spaced apron segment parts to hold them in spaced relation, and means are provided to maintain the spaced relation even in the event of failure of the hydraulic pressure.

United States Patent 1 1 [111 3,757,848

Scholz et a1. 1 Sept. 11, 1973 [54] METHOD AND APPARATUS TO RELIEVE 3,550,675 12/1970 1 Hess et a1. 164/282 THE STRAIN ()N ROLLER APRON 3,577,757 5/1971 Barten 72/237 SEGMENTS DURING CONTINUOUS FOREIGN PATENTS OR APPLICATIONS CASTING 2,023,002 11/1970 Germany... 164/282 [75] Ihventors: Heinrich'schblz,Grevefibfaifig 950,882 2/1964 Great Britain 164/282 Georg Bollig, Buederi'ch; Horst G th Kaa t; G h d Ott Primary Examiner-R. Spencer Annear Duesseldorf, all of Germany Attorney-Nichol M. Sandoe et a1.

[73] Assignee: Schloemann Alttiengesellschaft, [57] ABSTRAcT Duesseldorf, Germany In a continuous casting machine in which the casting Filed: 16, 1971 emerging from the moldis conducted through a sec- [21] AppL 2 2 ondary cooling zone by a guide apron having spaced apron segment parts between which the casting moves, means are provided for relieving overload stresses 1 Fo pp Priority Data which may be applied to said spaced apron segment Dec. 19, 1970 Germany", P 20 62 792.3 parts by said casting in the event of interruption of the casting process. Hydraulic pressure is applied to said [52] U.S. Cl 164/282, 72/237, 164/270 spaced. apron segment parts to hold them in spaced re- [51] Int. Cl B22d 11/12 lation, and means are provided to maintain the spaced [58] Field of Search 164/82, 282; 72/237 relation even in the event of failure of the hydraulic pressure. [56] 1 References Cited UNITED STATES PATENTS 13 Claims, 5 Drawing Figures 7 3,263,284 8/1966 Orr et a1. 164/154 r33 34 o o fi zy 23 g 2 t: r V /////////////1| II a 17-75] [4 .32 ":Fjj I i 5 i 5 I 1 o a SHEET 2 0F 3 FIG?) PAnzmsnsmmn I 757.848

sum 3 0F 3 Illr The invention relates to a method and an apparatus for relieving the strain on segments of a guide apron, located below the mold in the secondary cooling zone of a continuous casting machine in the event of a sudden cessation of the pouring process, when a part or all of the casting remains in the apron, wherein thespacing of opposing movable parts of the segments of the apron is controlled by the application to said parts of straining forces which press said parts against stops.

In conventional guide means for the casting, the apron below the mold is divided into segments comprising upper and lower parts. In order to support castings of varying cross sections effectively in such an apron, one part of each segment containing supporting elements such as rollers is arranged to be movable in a direction normal to the casting axis. Alternatively, both parts of each segment, located on opposite sides of the casting, may be movable. These segmentparts are usually moved by hydraulic cylinder units. For exactly adjusting the distance between moving parts on opposite sides of the segments of an apron, i.e., for making the adjustment to the cross section of the casting, adjustable or selectably insertable stops are provided. When the cross section of the casting is changed, first the corresponding stops are reset, and the parts of the apron segments are then forced against these stops. The straining pressure applied by the hydraulic cylinder units opposes the ferrostatic pressure of the liquid core of the casting. Therefore, the pressure applied to the segment parts by the hydraulic cylinder units, must always exceed the forces which are applied to the segment parts by the casting.

This type of guide apron has a number of drawbacks.

If the casting machine is-out of action for a longer period of time, due to an overflow of moltenmetal, a

power failure, a breakout of metal or a breakdown of the machines, the casting solidifies in the apron. To prevent the frozen shell of the casting, which is still thin in the upper portion of the apron, from re-melting, the cooling system must not be shut off until the casting is sufficiently solidified. Since, in a curved type casting machine, the cooling water cannot readily run off on the inside radius of the casting, whereas it runsoff at once on the outside radius, the inside of the arc of the casting will be more intensely cooled than the outside. Consequently, warping of the casting caused by'thermal strains may cause the casting to become jammed in the guideway of the apron. When the partly solidified casting is later withdrawn, theend'of the apron is sub,-

jected to considerable strain when the arc of the casting is straightenedoutand roller fracture or other damage to the apronmay occur. Damage may also be caused, principally when a metal breakout in the casting has occurred, because the'casting is then tightly gripped between the point where the metal break-out has taken place and the straightening rollers. When the ensuing shrinkage of the casting reduces the arc length between these two points where the casting is gripped, the segments of the apron may be subjected to an inadmissible overload. Furthermore, when the casting in the apron ceases to move, the thin frozen shell under theeffect of the internalferrostatic pressure, may begin to bulge between the supporting elements, which may cause damage to the supporting elements or the apron, when the casting is later withdrawn. l

A pressure failure in the hydraulic cylinders causes the guiding segments of the apron to open up, particularly when the guiding segments on both sides of the casting are movable. This'results in damage to the apron, particularly in the region close to the mold.

An object of the present invention is to eliminate the above described drawbacks and to provide a solution that requires lower casting straining forces, that will retain the movable apron parts in their position if the hydraulic pressure fails, and that nevertheless provides for the relief of overload on the apron which may be caused i.e. bysudden cessation of the metal pouring process. a

According to the method of the present invention, this is achieved in that the slackening of a principal straining force releases a force generated by the casting which causes an overload relief element to be displaced from its position, thereby increasing the spacing between the rollers.

This method prevents the apron from being damaged by forces generated by that part of the casting which remains motionless in the roller apron when pouring of metal suddenly ceases, and enables the partly solidified casting to be subsequently withdrawn without damage to'the apron. v

The apparatus for performing the method is charac terizedby the provision of an overload relief element between the principal straining element and the movable part of the segment of the apron.

Since, generally speaking, there is only little space available for the accommodation of attachments toroller aprons in continuous casting machines, it is desirable that the principal straining force should press against stops and have the same direction as the ferrostatic pressure of the casting, i.e., at right angles to the casting axis and directed away from it. The principal straining force is thus independent of the amount of the ferrostatic pressure and the spacing between opposing parts of segments of the apron is not changed by a rise or fall of the existing ferrostatic pressure. Hence a constant and invariant cross section is made available to the casting during operation owing to the rigid and inelastic delimitation of the movements of the movable part of the segment of the apron. v i

. If the overload relief element is'a wedge-shaped member associated with a second likewise wedgeshaped member, relative motion between these two wedge-shaped members resultsin varying distances between the outsides of the wedges. These varying distances are used for making a precise adjustment of the spacing between opposing parts of segments of the apron. The guide means, which are preferably columns for guiding the movable partsof the I segments, may have stops forsetting the spacing between the parts of the segments. Preferably these stops may have the form of rotatable stepped rings with cooperating and matching counter-members with corresponding projections.

Adjustments can be made for varying casting cross sections by rotation of the stepped .rings without having to replace any parts.

In order to facilitate adjustment of the segment spacing the-stepped rings may each be provided with a lever arm associated with locking means for locking the stepped rings in the position for the required spacing. According to a further feature of the present invention all the lever arms associated with the several apron segments of the roller apron may be interconnected for common operation and adjustment. The distance between the parts of the segments of an apron can be adjusted easily and reliably by these features.

By proper selection of the angle of inclination of cooperating wedge faces of the two wedges it is possible to accurately preselect the force needed to shift the overload relief element. However, it must be borne in mind that the wedge angle must exceed the existing limiting angle of friction.

In a preferred arrangement the wedges may be U- shaped so that they can embrace the columns. This will insure an unobstructed displacement of the overload relief element.

The locating force for the overload relief element during normal casting operation is transmitted from the principal straining element through an intermediate member having an inclined wedge face to a movable overload relief element which has a correspondingly inclined wedge face for cooperation with the intermediate member.

Depending on the selected location of the point where the principal strainingelement applies its force, another advantageous arrangement may consist in transmitting the locating force for the overload relief element from the principal straining element to the overload relief element via a cranked lever.

An embodiment of the present invention will hereinafter be described with reference to the drawings in which:

FIG. 1 is a cross section of a portion of a segment of a roller apron taken on the line I I in FIG. 3.

FIG. 2 is a front elevation of the arrangement for adjusting to a different casting cross section, and of an overload relief element.

FIG. 3 is a side elevation of a segment of the roller apron.

FIG. 4 is a horizontal section on the line IV IV of FIG. 2, and

FIG. 5 is a partial section corresponding to that of FIG. 1, showing a modified arrangement of the principal straining element.

Referring to FIGS. 1 to 4 a frame 1 carries the fixed apron segment part 2 and the movable apron segment part3, which is slidable on columns 9, of one segment of a roller apron. Part 2 of the segment comprises two end plates 4 mounted on frame 1, said end plates carrying bearings 5 for guide rollers 6. Instead of guide rollers 6, plates or other guide means may be used. Affixed to each end plate 4 is a guide sleeve 7, and cross members 8 connect the end plates 4. A pin 10 locates the column 9 inside the sleeve 7 which extends at right angles to the path of the casting. Slidably mounted on the column 9 is a further sleeve 11 which is secured to movable part 3 of the illustrated segment of the roller apron. Part 3 of the segment also includes end plates 13 carrying bearings 14 for rollers 15. Cross members 12 connect the end plates 13.

Located on one side of the sleeves 7 and 11 is a straining element in the form of a hydraulic cylinder unit 18. The piston rod 17 of this cylinder unit is attached to a bracket 16 secured to the sleeve 7. Affixed to the other end of the hydraulic cylinder 18 is a wedge 19. A pin 20 is fitted into this wedge 19, the projecting ends of the pin serving as pivots 21 for sliding blocks 22. The sleeve 11 is provided with brackets 23, 24

which carry a guide plate 25 which assures that the sliding blocks 22 are guided in the slotted hole 25 of plate 25 and hence the wedge 19 moves parallel to the column 9.

.- Resting on the sleeve 11 is a laterally slidably displaceable overload relief element 26 in the form of a wedge. The wedge face of this element 26 facing the wedge 19 has the same angle of slope as the opposed wedge face of the wedge 19. The element 26 is forked and straddles the column 9 which has plane areas machined into its sides in this region. The side of the element 26 which faces away from the top of the sleeve 11 is likewise provided with an inclined wedge face which slopes in relation to that side of said element which rests on the top of the sleeve 11. Located above the overload relief element 26 is yet another wedge-shaped element 27 of which the wedge face cooperates with the inclined wedge face of the overload relief element 26 that faces away from the sleeve 11. This element 27 is U-shaped and also embraces the column 9 which has alsoplane areas machined into its sides in this region.

Moreover, an adjusting screw 29 permits the lateral position of element 27 to be adjustably varied and fixed, which thereby determines precisely the distance between the opposing parts 2 and 3 of the segment of the roller apron. The adjusting screw 29 is held in a member 28. Mounted on the column 9 above the member 28 is a stepped ring 30 with several steps 30. The ring 30 is rotatable on the column 9. A groove 33 is machined into the upper end of the column 9 and this. groove is engaged by a divided cooperating stepped ring 34. For adjusting the spacing between the parts 2 and 3 of the apron segment the ring 30 is rotated into a different position and, in cooperation between the steps 30' of ring 30 and the corresponding matching projections 35 on ring 34, the cross section available for the casting is determined.

Furthermore, the stepped ring 30 carries a lever arm 31 which may be held by locking means 32 in specific positions corresponding to the required casting cross sections. The arms 31 associated with the several segments of the apron may be interconnected to permit all the segments along the length of the apron to be adjusted at once. I

Straps 36 which extend upwards to the member 28 are attached to each side of the sleeve 11. In the area of the member 28 each strap 36 has an elongated hole 37 for the reception of a pin 38 fitted to the-member 28. The straps ensure that the member 28 is pulled down when movable part 3 of the segment descends so that member 28 does not remain behind because of its asymmetric shape.

The overload relief elements are protected against fouling by covers 39.

In operation, pressure applied by the hydraulic cylinder 18 presses the sliding blocks 22 upwards against the brackets 23 which are attached to the sleeves ll of movable part 3 of the segment of the roller apronand thereby presses the sleeve 1 1 against the wedges 26 and 27. These in turn press against the member 28 and the stepped ring 30 and 34. At the same time the wedge 19 moves the overload relief element 26 towards the column 9, thereby causing the sleeve 11 to be locked in place by the pressure applied by the hydraulic cylinder 18.

If pouring of metal should cease with the concomitant risk of the casting becoming wedged in the roller apron or of segments of the apron being damaged by excessive strain, then the principal straining force applied by the hydraulic cylinder 18 is released, whereby the cylinder 18 and the attached wedge 19 may move downward by gravity only, or will be depressed when element 26 moves sideways from column 9. The wedge angle of the wedge face of overload relief element 26 which opposes the wedge face of element 27 is so chosen that when a predetermined force is generated by the casting and transmitted to the sleeve 11 which is not yetsufficient to cause damage, the overload relief element 26 will slide sideways away from column 9, so that movable part 3 is allowed to move upwards. The distance between parts 2 and 3 of the segment of the apron thus becomes greater and the segment is thus protected from damage by the increased force and the casting is also prevented from jamming between parts 2 and 3.

Furthermore, if the principal straining pressure which is applied by hydraulic cylinder 18 should decrease or be lost for any reason, then the overload relief element 26 will remain fixed and the distance between parts 2 and 3 of the segments of the apron will not change during normal operating conditions. Only large forces, such as may be generated by breakdown in the casting machine, cause the movable part 3 of the segment to be displaced upwards.

Normal operations can therefore continue even when the hydraulic cylinders 18 fail to apply pressure.

FIG. 5 shows a different embodiment of the movable part 3 of a segment of the roller apron. Frame 1 and the fixed part 2 of the apron segment are identical with the arrangement illustrated in FIGS. 1 and 3. The slidably movable guide sleeve 11 is provided with brackets 42. The piston rod 17 of the hydraulic cylinder 18 is attached to these brackets 42 by a pin 41. The other end of the hydraulic cylinder 18 is connected by a pin 44 to a cranked lever 43 which at one end is linked to a mounting 51 by pins 58. The mounting 51 is slidably fitted to the column9 and bears against a pin 55 on the end of column 9. The mounting 51 is attached to cross members 52 and straddles a wedge-shaped element 27, an overload relief element 26 and a rotatable stepped ring 30. For determining the operative position of the mounting 51 a ring 56 surrounds the pin 55 and is locked in position by a pin 57. The element 27 is slidably displaceable by means of an adjusting screw 29.

The cranked lever 43 and'the overload relief element 26 are connected by straps 47and pins 45 and 46. The distance between therollers 6 and in the segments of the apron is maintained by spacing pins 50 which cooperate with the stepped ring 30. For adjusting the distance between the rollers 6 and 15 the ring 30 is rotated into the desired position and the slidably movable part 3 of the segment is drawn towards the mounting 51 by the hydraulic cylinder 18. The force acting on the cranked lever 43 presses the overload relief element 26 in the direction of column 9 against the inclined wedge face of the element 27. The exact position of the elements 26 and 27 can be adjusted by the screw 29. The sleeve 1 1 is forced against the. pins 50 and the latter are pressed into the corresponding steps 49 of the stepped ring 30, which in turn is pressed downward by the overload relief element 26. If the load on the roller apron is to be reduced, the overload relief element 26 can be moved sideways towards cylinder 18 by applying the pressure to the piston in cylinder 18 in the opposite direction. Alternatively, the oil pressure in cylinder 18 can be relieved when the force which is generated by the casting within the apron segment exceeds a certain amount. This force will then push the element 26 sideways towards cylinder 18 thereby increasing the distance between rollers 6 and 15.

If it should be impossible, particularly in the event of a metal break-out, to withdraw the solidfied casting from the roller apron by means of the withdrawing machine, then the rings 34 in the embodiment shown in FIG. 1 or the rings 56 in the embodiment shown in FIG. 5 can be removed and the movable parts 30f the segments of the roller apron can be lifted off the casting by conventional means (not shown). 7

We claim as our invention:

1. In a continuous casting apparatus having an apron which guides the casting through a secondary cooling zone, said apron comprising a plurality of segments, each having opposed members engaging opposed surfaces of the casting, with at least one of said members movable with respect to the other member to accommodate castings of different thickness, means for relieving excessive forces on said opposed members in I the event of interruption of the casting operation, comprising a stop to limit the movement of said movable member, an overload relief element located adjacent said stop, means to apply pressure to said movable member to move it toward and hold it against said stop and to simultaneously move said overload relief element to lock said movable-member in adjusted position, and means actuated by said movable member upon release of said pressure and upon application by said casting of excessive forces thereto to move said overload relief element to release saidmovable mem her to permit further movement toward said stop.

2. Apparatus as claimed in claim 1 in which a column is mounted in fixed position on one of said opposed members and in which the other of said opposed memhers is in sliding engagement with said column.

3. Apparatus as claimed in claim 1 in which said means to apply pressure to said movable member includes a first wedge surface, and in which said overload relief element includes a second wedge surface located to be engaged by said first wedge surface in sliding relationship.

4. Apparatus as claimed in claim 3 in which said stop includes a third wedge surface, and in which said overload relief element includes a fourth wedge surface located to be engaged by said third wedge surfa'cein sliding relationship. l

5. Apparatus as claimed in-claim of inclination of the cooperating 4 in which the angle inclined surfaces of the wedges exceeds the existing limiting angle of friction.

6. Apparatus as claimed in claim 4 in which said third wedge surface is adjustable.

7. Apparatus as claimed in claim 2 in which said overload relief element and said stop are forked and straddle said column.

8. Apparatus as claimed in claim 2 in which said stop includes a first ring rotatably mounted on said column and having steps therein, anda second ring rotatably mounted on said column and having projections thereon to selectively engage said steps to adjust the effective position of said stop.

9. Apparatus as claimed in claim 1 in which said means to apply pressure to said movable member includes a cranked lever, and a link connecting one arm of said lever to said overload relief element.

10. Apparatus as claimed in claim 8 in which said stepped ring is provided with a lever arm which cooperates with locking devices for adjusting the ring to predetermined spacings between the opposing members of the segments of the apron.

11. Apparatus as claimed in claim 10 in which the lever arms of all the segments of the apron are interconnected for common operation and adjustment.

12. In a continuous casting apparatus having an apron which guides the casting through a secondary cooling zone, said apron comprising a plurality of segments, each having opposed members engaging pposed surface of the casting, with at least one of said members movable with respect to the other member to accommodate castings of different thickness, the

pressure applied to said movable member to move and hold it against a stop is applied in the same direction as the forces applied by the ferrostatic pressure of the casting. 

1. In a continuous casting apparatus having an apron which guides the casting through a secondary cooling zone, said apron comprising a plurality of segments, each having opposed members engaging opposed surfaces of the casting, with at least one of said members movable with respect to the other member to accommodate castings of different thickness, means for relieving excessive forces on said opposed members in the event of interruption of the casting operation, comprising a stop to limit the movement of said movable member, an overload relief element located adjacent said stop, means to apply pressure to said movable member to move it toward and hold it against said stop and to simultaneously move said overload relief element to lock said movable member in adjusted position, and means actuated by said movable member upon release of saId pressure and upon application by said casting of excessive forces thereto to move said overload relief element to release said movable member to permit further movement toward said stop.
 2. Apparatus as claimed in claim 1 in which a column is mounted in fixed position on one of said opposed members and in which the other of said opposed members is in sliding engagement with said column.
 3. Apparatus as claimed in claim 1 in which said means to apply pressure to said movable member includes a first wedge surface, and in which said overload relief element includes a second wedge surface located to be engaged by said first wedge surface in sliding relationship.
 4. Apparatus as claimed in claim 3 in which said stop includes a third wedge surface, and in which said overload relief element includes a fourth wedge surface located to be engaged by said third wedge surface in sliding relationship.
 5. Apparatus as claimed in claim 4 in which the angle of inclination of the cooperating inclined surfaces of the wedges exceeds the existing limiting angle of friction.
 6. Apparatus as claimed in claim 4 in which said third wedge surface is adjustable.
 7. Apparatus as claimed in claim 2 in which said overload relief element and said stop are forked and straddle said column.
 8. Apparatus as claimed in claim 2 in which said stop includes a first ring rotatably mounted on said column and having steps therein, and a second ring rotatably mounted on said column and having projections thereon to selectively engage said steps to adjust the effective position of said stop.
 9. Apparatus as claimed in claim 1 in which said means to apply pressure to said movable member includes a cranked lever, and a link connecting one arm of said lever to said overload relief element.
 10. Apparatus as claimed in claim 8 in which said stepped ring is provided with a lever arm which cooperates with locking devices for adjusting the ring to predetermined spacings between the opposing members of the segments of the apron.
 11. Apparatus as claimed in claim 10 in which the lever arms of all the segments of the apron are interconnected for common operation and adjustment.
 12. In a continuous casting apparatus having an apron which guides the casting through a secondary cooling zone, said apron comprising a plurality of segments, each having opposed members engaging opposed surface of the casting, with at least one of said members movable with respect to the other member to accommodate castings of different thickness, the method of relieving excessive forces on said opposed members in the event of interruption of the casting operation which comprises, applying pressure to said movable member in one direction to move and hold it against a stop, applying pressure to said movable member in another direction to lock it against said stop, and releasing both pressures simultaneously to unlock said movable member and to permit it to move toward said stop when said opposed members are subjected to excessive forces.
 13. A method according to claim 12 in which the pressure applied to said movable member to move and hold it against a stop is applied in the same direction as the forces applied by the ferrostatic pressure of the casting. 